/**
 * jquery.scrollFollow.js
 * Copyright (c) 2008 Net Perspective (http://kitchen.net-perspective.com/)
 * Licensed under the MIT License (http://www.opensource.org/licenses/mit-license.php)
 *
 * @author R.A. Ray
 *
 * @projectDescription        jQuery plugin for allowing an element to animate down as the user scrolls the page.
 *
 * @version 0.4.0
 *
 * @requires jquery.js (tested with 1.6.1)
 * @requires ui.core.js (tested with 1.8.13)
 *
 * @optional jquery.cookie.js (http://www.stilbuero.de/2006/09/17/cookie-plugin-for-jquery/)
 * @optional jquery.easing.js (http://gsgd.co.uk/sandbox/jquery/easing/ - tested with 1.3)
 *
 * @param speed                int - Duration of animation (in milliseconds)
 *                                                                 default: 500
 * @param offset                        int - Number of pixels box should remain from top of viewport
 *                                                                 default: 0
 * @param easing                string - Any one of the easing options from the easing plugin - Requires jQuery Easing Plugin < http://gsgd.co.uk/sandbox/jquery/easing/ >
 *                                                                 default: 'linear'
 * @param container        string - ID of the containing div
 *                                                                 default: box's immediate parent
 * @param killSwitch        string - ID of the On/Off toggle element
 *                                                                 default: 'killSwitch'
 * @param onText                string - killSwitch text to be displayed if sliding is enabled
 *                                                                 default: 'Turn Slide Off'
 * @param offText                string - killSwitch text to be displayed if sliding is disabled
 *                                                                 default: 'Turn Slide On'
 * @param relativeTo        string - Scroll animation can be relative to either the 'top' or 'bottom' of the viewport
 *                                                                 default: 'top'
 * @param delay                        int - Time between the end of the scroll and the beginning of the animation in milliseconds
 *                                                                 default: 0
 */

(function ($) {

    $.scrollFollow = function (box, options) {
        // Convert box into a jQuery object
        box = $(box);

        // 'box' is the object to be animated
        var position = box.css('position');

        function ani() {
            // The script runs on every scroll which really means many times during a scroll.
            // We don't want multiple slides to queue up.
            box.queue([ ]);

            // A bunch of values we need to determine where to animate to
            var viewportHeight = parseInt($(window).height());
            var pageScroll = parseInt($(document).scrollTop());
            var parentTop = parseInt(box.cont.offset().top);
//                        var parentHeight = parseInt( box.cont.attr( 'offsetHeight' ) );
//                        var boxHeight = parseInt( box.attr( 'offsetHeight' ) + ( parseInt( box.css( 'marginTop' ) ) || 0 ) + ( parseInt( box.css( 'marginBottom' ) ) || 0 ) );
            var parentHeight = parseInt(box.cont.outerHeight());
            var boxHeight = parseInt(box.outerHeight() + ( parseInt(box.css('margin-top')) || 0 ) + ( parseInt(box.css('margin-bottom')) || 0 ));

            var aniTop;

            // Make sure the user wants the animation to happen
            if (isActive) {
                // If the box should animate relative to the top of the window
                if (options.relativeTo == 'top') {
                    // Don't animate until the top of the window is close enough to the top of the box
                    if (box.initialOffsetTop >= ( pageScroll + options.offset )) {
                        aniTop = box.initialTop;
                    }
                    else {
                        aniTop = Math.min(( Math.max(( -parentTop ), ( pageScroll - box.initialOffsetTop + box.initialTop )) + options.offset ), ( parentHeight - boxHeight - box.paddingAdjustment ));
                    }
                }
                // If the box should animate relative to the bottom of the window
                else if (options.relativeTo == 'bottom') {
                    // Don't animate until the bottom of the window is close enough to the bottom of the box
                    if (( box.initialOffsetTop + boxHeight ) >= ( pageScroll + options.offset + viewportHeight )) {
                        aniTop = box.initialTop;
                    }
                    else {
                        aniTop = Math.min(( pageScroll + viewportHeight - boxHeight - options.offset ), ( parentHeight - boxHeight ));
                    }
                }

                // Checks to see if the relevant scroll was the last one
                // "-20" is to account for inaccuracy in the timeout
                if (( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 )) {
                    box.animate(
                        {
                            top: aniTop
                        }, options.speed, options.easing
                    );
                }
            }
        };

        // For user-initiated stopping of the slide
        var isActive = true;

        if ($.cookie != undefined) {
            if ($.cookie('scrollFollowSetting' + box.attr('id')) == 'false') {
                var isActive = false;

                $('#' + options.killSwitch).text(options.offText)
                    .toggle(
                    function () {
                        isActive = true;

                        $(this).text(options.onText);

                        $.cookie('scrollFollowSetting' + box.attr('id'), true, { expires: 365, path: '/'});

                        ani();
                    },
                    function () {
                        isActive = false;

                        $(this).text(options.offText);

                        box.animate(
                            {
                                top: box.initialTop
                            }, options.speed, options.easing
                        );

                        $.cookie('scrollFollowSetting' + box.attr('id'), false, { expires: 365, path: '/'});
                    }
                );
            }
            else {
                $('#' + options.killSwitch).text(options.onText)
                    .toggle(
                    function () {
                        isActive = false;

                        $(this).text(options.offText);

                        box.animate(
                            {
                                top: box.initialTop
                            }, 0
                        );

                        $.cookie('scrollFollowSetting' + box.attr('id'), false, { expires: 365, path: '/'});
                    },
                    function () {
                        isActive = true;

                        $(this).text(options.onText);

                        $.cookie('scrollFollowSetting' + box.attr('id'), true, { expires: 365, path: '/'});

                        ani();
                    }
                );
            }
        }

        // If no parent ID was specified, and the immediate parent does not have an ID
        // options.container will be undefined. So we need to figure out the parent element.
//                if ( options.container == '')
//                {
//                        box.cont = box.parent();
//                }
//                else
//                {
//                        box.cont = $( '#' + options.container );
//                }
        box.cont = box.parent();

        // Finds the default positioning of the box.
        box.initialOffsetTop = parseInt(box.offset().top);
        box.initialTop = parseInt(box.css('top')) || 0;

        // Hack to fix different treatment of boxes positioned 'absolute' and 'relative'
        if (box.css('position') == 'relative') {
            box.paddingAdjustment = parseInt(box.cont.css('paddingTop')) + parseInt(box.cont.css('paddingBottom'));
        }
        else {
            box.paddingAdjustment = 0;
        }

        // Animate the box when the page is scrolled
        $(window).scroll(function () {
                // Sets up the delay of the animation
                $.fn.scrollFollow.interval = setTimeout(function () {
                    ani();
                }, options.delay);

                // To check against right before setting the animation
                box.lastScroll = new Date().getTime();
            }
        );

        // Animate the box when the page is resized
        $(window).resize(function () {
                // Sets up the delay of the animation
                $.fn.scrollFollow.interval = setTimeout(function () {
                    ani();
                }, options.delay);

                // To check against right before setting the animation
                box.lastScroll = new Date().getTime();
            }
        );

        // Run an initial animation on page load
        box.lastScroll = 0;

        ani();
    };

    $.fn.scrollFollow = function (options) {
        options = options || {};
        options.relativeTo = options.relativeTo || 'top';
        options.speed = options.speed || 500;
        options.offset = options.offset || 0;
        options.easing = options.easing || 'swing';
        options.container = options.container || this.parent().attr('id');
        options.killSwitch = options.killSwitch || 'killSwitch';
        options.onText = options.onText || 'Turn Slide Off';
        options.offText = options.offText || 'Turn Slide On';
        options.delay = options.delay || 0;

        this.each(function () {
                new $.scrollFollow(this, options);
            }
        );

        return this;
    };
})(jQuery);